1. Field of the Invention
The present invention relates to a speech signal processing apparatus, and more particularly, to a signal detection apparatus for detecting a noise-suppressed speech signal from a noisy speech signal and detecting a kind of the detected speech signal, a signal processing apparatus for discriminating between speeches of plural speakers prior to speech recognition, and a speech recognition apparatus for recognizing a speech spoken by a speaker.
2. Description of the Prior Art
Conventionally, there has been suggested an apparatus for discriminating between a speech and a noise in response to a noisy speech signal (See, for example, the Japanese patent laid open publication (JP-A) No. 59-124397/1984, and the Japanese patent laid open publication (JP-A) No. 59-131997/1984). The discrimination result outputted from the apparatus is used in an apparatus for recognizing a speech such as a speech recognition apparatus. However, the conventional apparatuses for discriminating between a noise and a speech can not detect a kind of the speech, namely, can not detect who speaks. In a general speech recognition apparatus, it is desired that a kind of the speech is previously detected.
Further, conventionally, in a conventional speech recognition apparatus, a word spoken by a speaker is often recognized by inputting a speech signal of a particular speaker thereto. Namely, in order to heighten a recognition rate upon pattern-matching of speech features, information as to who now speaks is inputted to the speech recognition apparatus. Alternatively, in a speech recognition apparatus provided in a system for keeping information confidential it is desired that only a particular speech is accepted. Namely, it is desired to judge who speaks and to use information of the judgment result prior to speech recognition.
Further, recently, there has been developed a system which can be used only if a particular word is spoken in secured areas such as a laboratory. In this system, by utilizing a speech recognition technique, when a key word is spoken toward this system using key words such as "one", "three", "five", "seven", this system is enabled. In the system of this type, it is necessary not only to use the above-mentioned key word but also to limit the speaker to a particular one. Namely, it is desired that the system is constituted so that the system is enabled only when a predetermined particular speaker speaks a key word toward the system.